Mechanical/electrical displacement transducer

ABSTRACT

Displacement measuring apparatus for measuring the displacement and movement of an object includes a sensor having an operative surface and circuitry for producing an electrical output signal whose value is dependent upon the area of the operative surface covered by an electrical/magnetic field producing member. The apparatus also includes an elongate, flexible band capable of producing an electric/magnetic field, where the band is attached at one end to the sensor to roll over and cover or unroll from over and uncover the operative surface as the object whose displacement is to be measured is moved. The value of the electrical output signal produced by the circuitry is thus dependent upon the area of the operative surface covered by the band and thus by the position and movement of the object.

This application is a divisional of application Ser. No. 08/183,280filed Jan. 18, 1994, now U.S. Pat. No. 5,957,368 which is a divisionalof application Ser. No. 028,767 filed Mar. 9, 1993, now U.S. Pat. No.5,302,886 issued Apr. 12, 1994, which is a continuation of applicationSer. No. 07/417,181 filed Oct. 4, 1989, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates in general to apparatus for sensing displacementor position of an object, and in particular to apparatus which utilizesa flexible moveable band or other moveable element to convert a physicalmeasure of displacement and position of an object into an electricalsignal representing such measure.

In the operation of various mechanical and electro-mechanical systems,it is necessary to monitor the position and displacement of either someelement of the system or some object which is not part of the system.For example, in robotic systems (a technology whose use is dramaticallyincreasing) it is almost always necessary to monitor and control themovement and position of various component parts of the systems, such asan arm, fingers or other grasping elements, etc. Such monitoring andcontrol yields the dexterity and precision required for a robotic systemto carry out its functions.

Prior art mechanisms for sensing position and displacement have mostoften utilized a direct connection between the article or object whoseposition or displacement was to be monitored, and some type of gauge,needle or other visual indicator. Movement of the article or objectwould thus cause a corresponding movement of the gauge or needle. Asexpected, such mechanisms have typically been large and cumbersome andhave lacked precision in carrying out the monitoring function. Further,since some type of sliding action of some part of the measuringmechanism typically was involved, friction was present which, of course,resulted in wear.

Although electronic apparatus for measuring position and displacementhas come into greater use in recent years and has at least partiallysolved the bulkiness and imprecision problems of the prior artmechanisms, such apparatus has been complicated in design and, as aresult of such complication, generally lacking in reliability. Also, thecontact friction and attendant wear generally remained.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a simple, efficient andreliable apparatus for measuring position and movement of a component orarticle.

It is another object of the invention to provide such apparatus which iscompact and contains few moving parts.

It is a further object of the invention to provide such apparatus whichavoids the need for sliding, friction-producing components.

It is also an object of the invention to provide such apparatus which iswell-suited for use with semiconductors and integrated circuits.

It is still another object of the invention to provide such apparatuswhich can be fabricated utilizing conventional integrated circuitfabrication technology for at least part of the apparatus.

The above and other objects of the invention are realized in onespecific illustrative embodiment of displacement measuring apparatusadapted for measuring position and movement of an object. Thedisplacement measuring apparatus includes a sensor (or plurality ofsensors), formed with at least one surface area, for producing anelectrical output signal whose value varies with variation in theproximity of a band element to the surface area, and an elongate,flexible band disposed in proximity with the surface area so that atleast a portion of the band is caused to selectively roll over and coveror unroll from over and uncover at least a portion of the surface areawhen the object is moved. Movement and position of the object, whichcauses the band to roll over or unroll from over the surface area of thesensor, is thus determined by the electrical signal produced by thesensor (or sensors).

In accordance with one aspect of the invention, some portion of the bandis fixed relative to the sensor and some other portion is coupled to theobject. Movement of the object toward or away from the surface area ofthe sensor, or generally parallel therewith, will cause the band tochange its location relative to the surface area and this change isdetected by the sensor.

In accordance with another aspect of the invention, a voltage issupplied to the band to cause it to produce an electric field and thesensor is comprised of a field-effect transistor for detecting themagnitude of the electric field produced by the band and thus theproximity of the band to the field-effect transistor. Alternatively, theband may be magnetized and the sensor may comprise a split-drainmagnetic field-effect transistor for detecting the strength of themagnetic field developed by the band and thus the position of the bandrelative to the magnetic field-effect transistor. Other sensorconfigurations, for example utilizing the Hall effect, capacitivesensing, optical sensing and sonar sensing, may also be employed todetect the movement and location of the bands to thus detect themovement and location of the object. In addition, the sensor area ofsensitivity may be constructed to allow for producing a signal whosevalue varies in a predetermined (linear or nonlinear) way with movementof the band.

In accordance with still another aspect of the invention, a displacementmeasuring device utilizes a magnetized or electrically charged rotatableor linearly moveable element coupled to the object whose position is tobe measured, and an array of magnetic field or electric field detectorsto detect the position of the element and thus of the object.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the inventionwill become apparent from a consideration of the following detaileddescription presented in connection with the accompanying drawings inwhich:

FIGS. 1A, 1B and 1C are perspective, side elevational and fragmented endperspective views respectively of displacement measuring apparatusutilizing a field-effect transistor in accordance with the principles ofthe present invention;

FIG. 2 is a fragmented end perspective view of displacement measuringapparatus utilizing capacitive coupling in accordance with the presentinvention;

FIG. 3 is a perspective view of displacement measuring apparatusutilizing a split-drain magnetic field-effect transistor in accordancewith the present invention;

FIG. 4 is a perspective view of displacement measuring apparatusutilizing an electret sheet and a field-effect transistor in accordancewith the present invention;

FIG. 5 is a perspective view of displacement measuring apparatusutilizing the Hall effect in accordance with the present invention;

FIG. 6 is a side, elevational view of displacement measuring apparatusutilizing capacitance variation to detect movement of an object inaccordance with the present invention;

FIG: 7 is a side, elevational view of displacement measuring apparatusutilizing a continuous band for measuring two degrees of freedommovement of an object in accordance with the present invention;

FIG. 8 is a perspective view of displacement measuring apparatusutilizing two continuous bands for measuring movement of a joystick inaccordance with the present invention;

FIGS. 9A and 9B show respectively an isometric view and side,elevational view of rotational displacement measuring apparatus made inaccordance with the present invention;

FIGS. 10A and 108 show respectively a perspective view and a side,elevational view of an alternative embodiment of a continuous rotationaldisplacement measuring apparatus made in accordance with the presentinvention;

FIG. 11 is a side, elevational view of apparatus for measuringrotational displacement of a cylinder in accordance with the presentinvention;

FIG. 12 is a side, elevational view of another embodiment of apparatusfor measuring rotational displacement of a cylinder in accordance withthe present invention;

FIG. 13 is a side, elevational view of displacement measuring apparatusfor measuring two degrees of freedom of linear movement of an object andanother degree of freedom of rotational movement of the object, inaccordance with the present invention;

FIG. 14 is a perspective view of displacement measuring apparatus forproducing a digital output representing the position and movement of anobject, in accordance with the present invention;

FIG. 15 is a perspective view of displacement apparatus for producingdiscrete output increments in response to movement of an object, inaccordance with the present invention;

FIG. 16 is a perspective view of displacement measuring apparatus forproducing a nonlinear output in response to movement of an object, inaccordance with the present invention;

FIG. 17 is a perspective view of displacement measuring apparatusutilizing a linearly moveable, wedge-shaped element;

FIG. 18 is a perspective view of another rotational displacementmeasuring apparatus made in accordance with the present invention;

FIG. 19 is a perspective view of still another rotational displacementmeasuring apparatus made in accordance with the present invention;

FIG. 20 is a perspective view of displacement measuring apparatusutilizing optical sensing in accordance with the present invention;

FIG. 21 is a perspective view of another embodiment of displacementmeasuring apparatus utilizing optical sensing;

FIG. 22 is a side elevational view of still another displacementmeasuring apparatus utilizing optical sensing;

FIG. 23 is a side, elevational view of displacement measuring apparatusutilizing acoustic sensing;

FIG. 24 is a graphic view of displacement measuring apparatus of thepresent invention utilized for weighing;

FIG. 25 is a side, elevational view of displacement measuring apparatusof the present invention utilized for temperature measurement;

FIG. 26 is a side, elevational view of displacement measuring apparatusof the present invention used for measuring the angle between twoelements pivotally joined together at their ends;

FIG. 27 is a side, elevational view of displacement measuring apparatusof the present invention utilized also for weighing;

FIG. 28 is a side, elevational view of displacement measuring apparatusof the present invention utilized for measuring acceleration;

FIG. 29 is a side, elevational view of displacement measuring apparatusof the present invention utilized for measuring velocity;

FIG. 30 is a perspective view of displacement measuring apparatusutilizing electrical resistance variation to detect movement of anobject in accordance with the present invention;

FIG. 31 is a perspective view of another embodiment of displacementmeasuring apparatus utilizing electrical resistance variation to detectmovement of an object; and

FIG. 32 is a side, elevational view of displacement measuring apparatusof the present invention utilized for measuring, among other things,acceleration and other force producing phenomena.

DETAILED DESCRIPTION

Referring to FIGS. 1A, 1B and 1C, there is shown one illustrativeembodiment of a band-controlled transducer or sensor for measuring twodegrees of freedom of movement of an object 4. The object 4 (which issimply in the form of a plate in FIGS. 1A through 1C) may take any shapeor form and could be a part of a robotic system, or other mechanicalstructure for which the part's position and movement is to bedetermined. The object 4 is attached to one end of an elongate,flexible, electrically conductive band 8. The other end of the band 8 isaffixed, by a suitable adhesive, pin or other fastening means, to oneend of a substrate 12 made, for example, of silicon and having an uppergenerally planar surface in which are disposed the operating parts of asensor for sensing the position of the band 8. The band 8 is coupled toa voltage source 16 to enable it to produce an electric field.

Disposed on and formed, for example, by conventional microfabricationtechniques on the upper surface of the substrate 12 is a field-effecttransistor (FET) 20. The FET 20 is a well-known semiconductor device andincludes a conductive source region 24 formed in the substrate 12, aconductive drain region 28 spaced from and formed to be generallyparallel with the source region, and a conductive channel region 32disposed between the source region and drain region. A layer ofinsulation 36 is disposed over the upper surface of the substrate 12 andover the source, drain and channel regions 24, 28 and 32.

The source region 24 and drain region 28 are maintained at differentelectric potentials by a voltage source 34 so that electric current iscaused to flow between the regions through the channel 32. Theconductivity of the channel region 32 is affected by electrical charges(or an electric field) located in close proximity to the channel region.Thus rolling and unrolling the band 8 over the insulation layer 36 toselectively cover and uncover the FET 20 will vary the magnitude of theelectrical current being conducted through the channel region 32 anddetected by a meter (ammeter) 38. The band 8 effectively acts as thegate of the FET 20 to control the flow of electrical current between thesource region 24 and the drain region 28. Measuring this current flowcan thus provide a measure of the rolling and unrolling of the band 8and thus a measure of the position and movement of the object 4. Afurther discussion of the operation of FETS is found in U.S. Pat. No.4,767,973, issued Aug. 20, 1988, and incorporated herein by reference.

The band 8 might be constructed of any suitably flexible, electricallyconductive material such as copper foil, aluminum foil, metalizedpolymer film, metalized quartz, metalized thin silicon, etc.Advantageously, the band 8 is formed so that its lateral edges curvedownward slightly toward the substrate 12 (when overlaying thesubstrate) so that the band will roll over and unroll from theinsulation layer 12 in a consistent, nonsliding fashion to maintaincontact with the insulation layer. Electrostatic attraction can also beused to hold the band 8 snugly against the insulation layer 12.

The band 8 and substrate 12, with component parts, may all be fabricatedusing microfabrication techniques. The band 8, for example, could besputter deposited over the substrate 12 and then photolithographicallyetched to define the desired size and shape. An etchant could also beused to release a portion of the band from the substrate and allow it tocure away from the substrate.

An alternative to utilizing a conductive band 8 connected to a voltagesource 16 is to provide a band of material containing positive ornegative charges. For example, the band 8 could illustratively be formedfrom flexible polytetrafluoroethylene with electrons implanted therein.

Another alternative to the FIGS. 1A through 1C embodiment would be toinclude a layer of conductive material between the layer of insulation36 and the substrate 12 and then position the FET 20 remotely from theband 8 contact region. This conductive layer or gate would beelectrically coupled to the gate of the remote FET so that rolling theband 8 over the insulation layer 36 would induce an electrical charge onthe surface of the conductive layer located under the insulation strip36 and this electrical charge would be reflected in the gate of theremote FET to affect the conductivity of the channel region of the FET.A measure could then be made of the proximity of the band 8 over theinsulation layer 36 and thus of the position and movement of the object4.

FIG. 2 shows an alternative embodiment of a band-controlled displacementmeasuring device which utilizes capacitive coupling in conjunction withan FET. In this embodiment, a substrate 40 carries the source, channeland drain regions of an FET 44 at the upper surface and near one side ofthe substrate (similar to the FIG. 1A through 1C embodiment) and aconductive strip of material 48, arranged generally in parallel with thesource, drain and channel regions of the FET 44, near the other side ofthe substrate. Coupled to the conductive strip 48 is an AC electricalvoltage source 52. A dielectric layer of material 56 is disposed on theupper surface of the substrate 40 and over the FET 44 and conductivestrip 48. A flexible, electrically isolated, conductive band 60 is thendisposed to roll over and unroll from over the dielectric layer 56 as anobject or component to which the band is coupled is caused to move.

The signal supplied by the voltage source 52 to the conductive strip 48develops a capacitance between the conductive strip and the band 60 andthis capacitance, of course, results in the development of a charge onthe band and this charge affects the conductivity of the channel regionof the FET 44. As the band 60 is rolled over and unrolled from thedielectric layer 56, the capacitance is caused to change, changing theaffect on the FET 44 and the conductivity of the channel region thereof.As with the FIGS. 1A through 1C embodiment, the change in conductivityof the channel region can be monitored as a determination of themovement and position of the band 60 and thus of an object or componentcoupled to the band.

FIG. 3 shows a perspective view of displacement measuring apparatusutilizing a split-drain magnetic field-effect transistor (MAGFET) 64.The MAGFET 64 is formed on the upper surface of a substrate 68 andincludes a source region 72 coupled to a D.C. current source 76, twodrain regions 80 and 84, and a conductive channel region 88 disposedbetween the source region and the two drain regions. A flexible,magnetizable band 92 is disposed on the substrate 68 to selectivelycover and uncover the channel region 88. A layer of insulation 96 could,but need not necessarily, be disposed over the MAGFET 64 and under theband 92.

In the absence of a magnetic field impinging upon the channel region 88,current flows from the source region 72 through the channel region 88equally to the two drain regions 80 and 84. When a magnetic field ispresent, such as when the magnetized band 92 is at least partiallyoverlying the channel region 88, the current through the channel regionis deflected to flow more to one drain region than the other, with themagnitude of the deflection and thus the imbalance of current flowing tothe two drain regions being dependent upon the intensity of the magneticfield. This intensity, of course, will depend on what portion of thechannel region 88 is covered by the band 92 and so by measuring thecurrent imbalance in the two drain regions 80 and 84, a measure of thedisplacement of the band and thus of an Object to which the band iscoupled can be made. The band 92 might illustratively be made of a thinfilm of alnico alloy (aluminum, nickel, cobalt and sometimes copper),alloy of nickel and cobalt, samarium cobalt, ferric oxide, ferricchromium, chromium dioxide, etc., appropriately magnetized.

FIG. 4 is a perspective view of displacement measuring apparatus whichutilizes an electret sheet of material 100 in which are implanted ordisposed electrons. The electret sheet 100 is positioned over andattached to a substrate 104 in which is formed an FET 112 in a fashionsimilar to that described for FIGS. 1A through 1C. Positioned to moveover and cover and move from over and uncover the electret sheet 100 isa flexible conductive band 108. The band 108 is attached at one end tothe electret sheet 100 and is coupled to a ground potential 116. Theother end of the band 108 is joined to an object or element whoseposition is to be measured.

The device of FIG. 4 operates using a "capacitive divider" effect inwhich the electric field produced by the electret sheet 100 is directeduniformly outwardly from the sheet when the band 08 is not in closeproximity, and is directed towards the band when the band is in closeproximity. Thus, the electric field of the electret sheet 100 will bedirected towards the FET 112 to affect the conductivity of the channelregion thereof when the band 108 is curled away from the sheet, and willbe redirected away from the FET 112 and towards the band 108 when theband is in position over the sheet. Thus the conductivity of the channelregion of the FET. 112 is determined by the proportion of the electretsheet 112 covered by the band 108. In a manner already described, thedevice of FIG. 4 could thus be used to measure movement and position ofan object.

The electret sheet 100 might illustratively be made ofpolytetrafluoroethylene, charged with electrons.

FIG. 5 is a perspective view of another embodiment of displacementmeasuring apparatus where the well-known Hall effect is utilized. Theapparatus includes a substrate of conductive material 120, such ascopper alloys, aluminum alloys, etc. A current source 124 suppliescurrent to one end of the substrate 120 to flow therethrough to theother end. A series of pairs of electrodes 128 are positioned onopposite sides along the length of the substrate 120 and are coupled toa detector 132. A magnetized, flexible band 136 is attached at one endto one end of the substrate 120 to selectively roll over and unroll fromover the substrate as earlier described.

In accordance with the Hall effect, current flowing in a conductor isdeflected from one side of the conductor towards the other side when theconductor is subjected to a magnetic field. Thus in the FIG. 5 device,when the magnetized band 136 is overlying a portion of the substrate120, the current flowing from one end of the substrate to the other isdeflected at that portion but is not deflected at the portion which isnot overlaid by the band. This current deflection, in the form of avoltage drop, is detected by the detector 132 to provide a measure ofthat portion of the substrate 120 which is covered by the band 136 andthus a measure of the movement of an object or component to which thefree end of the band 136 is coupled.

FIG. 6 is another embodiment of a displacement sensing device made inaccordance with the present invention. This device includes a pair ofconductive plates 140 and 144 spaced apart a distance D and coupled to avoltage source and detector 148. Two dielectric layers 152 and 156 aredisposed on the facing surfaces of plate 140 and 144 respectively asindicated. A pair of elongate, flexible and conductive bands 160 and 164are each joined at one end to a side of a respective dielectric layer152 and 156 to extend forwardly along the respective layer and theninwardly and rearwardly where the other ends of the ends are joinedtogether, as shown in FIG. 6. The other ends of the bands 160 and 164are coupled to an object 168 whose position and movement is to bedetected. As the object moves toward a position between the plates 140and 144, more of the bands 160 and 164 are caused to roll over andoverlay dielectric layers 152 and 156 respectively. Of course, as theobject 168 moves in a direction away from between the plates 140 and144, the bands 160 and 164 are unrolled from covering respectivedielectric layers. Movement of the object 168 and thus movement of thebands 160 and 164 causes a variation in the capacitance between theplates 140 and 144 which variation is measured by the A.C. voltagesource and detector 148, which for example could include an ammeter. Theeffective configuration of the capacitor plates is graphicallyillustrated at 172 for the situation where the bands 160 and 164 havebeen unrolled from between the plates 140 and 144. The effectivecapacitor configuration for the situation when the bands 160 and 164 arerolled between the plates 140 and 144 is illustrated at 176. The graphicrepresentations 172 and 176 show the effective difference in capacitancefor when the bands 160 and 164 are between the plates 140 and 144 versuswhen the bands are not between the plates. Thus, variation in thecapacitance between the plates 140 and 144 provides a measure of themovement and position of the object 168 as desired.

An alternative capacitive measuring device to FIG. 6 involves the use ofonly one band, for example band 160, and provision of only oneconducting plate, for example plate 144, with the other plate, forexample plate 140, being nonconductive. Then, the voltage source anddetector 148 would still be connected to plate 144, and also band 160 todevelop a capacitance between the plate 144 and band 160. Thiscapacitance would vary as the band 160 was rolled over or unrolled fromover the nonconductive plate 140, caused by movement of the object 168to thereby provide a measure of the position and movement of the object.

FIG. 7 is a side, elevational view of displacement apparatus utilizing acontinuous band to measure two degrees of freedom of movement of anobject 180. The apparatus includes a substrate 184 having two FETsensors 188 and 192 linearly spaced apart in the upper surface of thesubstrate. An insulation layer 196 is positioned on the substrate 184over the FET sensors 188 and 192. A flexible conductive band 200 isformed into a loop and disposed on the insulation layer 196 to toll backand forth over a locus on which the FET sensors 188 and 192 aredisposed.

When the object 180 is moved to the right in FIG. 7, the band 200 iscaused to also roll to the right to cover FET sensor 192 and to uncoverFET sensor 188. This movement, of course, is detectable by the sensorsto provide an indication of both the direction of movement of the object180 and the magnitude of the movement. If the object 180 is movedupwardly, the band 200 is caused to unroll from both sensors 188 and 192and this also is detectable. Movement of the object 180 to the left ordownwardly can be detected in a similar fashion so that movement to theright or left, and up or down of the object 180 can be readily detected.The band 200, of course, would carry an appropriate charge so as toproduce an electric field either from a voltage source or from chargesembedded in the band.

Although the FIG. 7 device was described as utilizing FET sensors, itshould be understood that other type sensors described earlier couldalso be utilized such as MAGFETs, capacitive coupling, electret sheets,and Hall effect sensing.

FIG. 8 is a perspective view of displacement measuring apparatus formeasuring the position and movement of a joystick 204. The apparatusincludes a substrate 208 on the surface of which are located four FETsensors 212, 216, 220 and 224, positioned along intersecting imaginarylines as shown. An insulation layer 228 is disposed on the substrate 208over the four sensors. Disposed on the substrate 208 are two flexible,electrically conductive bands 232 and 236 both formed into loops anddisposed crosswise of one another. The joystick 204 is pivotally affixedin the substrate 208 to extend upwardly through openings in the bands232 and 236, including openings 240 formed in band 236 and opening 244formed in band 232. To allow movement of the joystick 204 withoutbending either of the bands 232 and 236 sideways, the openings 240 and244 are formed crosswise in the respective bands and crosswise withrespect to one another as shown in FIG. 8. Thus, the joystick 204 may bemoved toward sensor 216 or sensor 224 to thereby move the band 232without bending the band 236 sideways. Similarly, the joystick may bemoved towards sensor 212 or sensor 220 to move band 236 without bendingband 232 sideways. Such movement of the joystick 204 and thus of thebands 232 and 236 is detected by the particular sensors affected whenthe sensors are covered or uncovered as described for earlierembodiments.

Again, the bands 232 and 236 would be charged to produce electric fieldsas described for earlier embodiments. Also, the bands 232 and 236 mightadvantageously be secured at lower sections to the substrate 208.Finally, other sensing arrangements described earlier could also be usedwith the FIG. 8 device.

FIGS. 9A and 9B show respectively an isometric view and a sideelevational view of apparatus for measuring rotational displacement of ashaft 250. The shaft 250 is mounted to rotate in substrate 254 in whichis disposed in an annular configuration an FET sensor 258 havingconventional source, drain and channel regions. An insulation layer 262is positioned on the substrate 254 over the FET sensor 258. A disk 266is mounted on the shaft 250 adore the substrate 254 to rotate as theshaft is rotated. A flexible, electrically conductive band 270 isattached at one end to the insulation layer 262 and at the other end tothe bottom of the disk 266 so that when the shaft 250 is rotated in onedirect[on (for example, clockwise looking down on the device), the bandis caused to lay down over the sensor 258, and when rotated in theopposite direction, the band is pulled up from over the sensor.Rotational movement and position of the shaft 250 can thus be detectedby the sensor 258.

The displacement measuring apparatus shown in FIGS. 10A and 10B utilizea continuously formed band 280 folded over itself to contact both theupper surface of an insulation layer 284 disposed over a substrate 288,and the underneath surface of a disk 292 mounted to rotate with a shaft296. The shaft 296 is mounted to rotate in the substrate 288. An FETsensor 30 is formed generally in a circle as best seen in FIG. 10A sothat as the shaft 296 and thus the disk 292 are rotated, that portion ofthe band 280 which is in contact with the disk 292 is carried with thedisk so that the lower portion of the band progressively covers anduncovers different portions of the sensor 300. The band 280 mightillustratively be affixed to the lower surface of the disk 292 althoughwith appropriately fabricated bands, the holding of the band 280 to theunderneath surface of the disk could be accomplished by electrostaticattraction, surface tension with a thin film of liquid, magnetization,etc. When the band 280 is not attached either to the disk 292 or theinsulation layer 284, it is self-aligning in the radial direction, i.e.,it will automatically space itself uniformly about the shaft 296. Thedevice of FIGS. 10A and 10B, of course, provides foe measuring angularposition and movement of the shaft 296 as the band 280 is caused tocover and uncover different portions of the sensor 300. Other types ofsensors as discussed above could also be utilized in lieu of the FETsensor 300, and in lieu of the FET sensor 258 of FIG. 9A.

FIGS. 11 and 12 show embodiments of apparatus for measuring the angularmovement and displacement of cylinders 304 and 324 respectively. Thecylinder 304 in FIG. 11 includes conductive plates 306 and 308 formed orattached to the exterior of the cylinder. A hollow cylinder 310 isdisposed about the exterior of rotatable cylinder 304, but is spacedtherefrom in fixed position. A pair of plates 312 and 314 are carried onthe inside surface of the hollow cylinder 30 and spaced apart as shown.Plates 306, 308, 312 and 314 all include a dielectric layer of materialon their exposed facing surfaces. Two flexible, electrically conductivebands 316 and 318, formed into loops, are disposed between the cylinder304 and the cylinder 310 to roll over the interior surface of thecylinder 310 and the exterior surface of the cylinder 304 as thecylinder 304 is rotated about a fixed axis 320. In a manner similar tothat described for the FIG. 6 apparatus, the capacitance developedbetween plates 306 and 314 and plates 308 and 312 varies as the bands318 and 316 respectively move between or out from between the respectiveplates so that measuring the capacitance provides a measure of therotational displacement and movement of the cylinder 304.

Other sensor configurations could also be used in the FIG. 11 structureincluding FETs, MAGFETs, electret sheets, etc.

In the FIG. 12 embodiment, as the cylinder 324 is rotated about a fixedaxis 325, it causes a band 326 formed into a loop to roll back and forthon the surface of a substrate 328 in which is disposed in a linearlyspaced-apart relationship two FET sensors 330 and 332. The position ofthe band 326, detected by the sensors 330 and 332, thus provide anindication of the rotational position of the cylinder 324.

FIG. 13 is a side, elevational view of displacement measuring apparatusfor measuring two linear degrees of freedom of movement of a plate 350and one degree of freedom of rotational movement of the plate. Theapparatus includes a substrate 354 in which are formed on the uppersurface thereof two linearly spaced-apart sensors 356 and 358. The plate350 likewise includes at its lower surface two linearly spaced-apartsensors 360 and 362. A flexible, electrically conductive band 364 formedinto a loop is positioned between the plate 350 and substrate 354 toroll back and forth laterally and selectively cover and uncover thesensors 356,358,362 and 360 which accordingly produce electrical outputsrepresenting the, amount of coverage by the band. This, of course,provides a reading or measure of the location and movement of the plate350. The sensors 356, 358, 360 and 362 could take a variety of forms asearlier discussed.

FIG. 14 is a perspective view of displacement measuring apparatus forproducing a digital output signal representing position of a flexibleband 370 and thus of an object 374 to which the band is attached. Asubstrate 378 includes a plurality of sensors 382 positioned at selectedintersections of an imaginary grid on the surface of the substrate sothat as the band 370 is rolled over the substrate, differentcombinations of sensors are affected and these combinations producebinary coded output signals. For example, if only sensor 382 werecovered by the band 370, then that sensor would produce an output signalwhich would represent the numeral 8. If the band 370 were moved to alsocover sensors 382b, then they would produce output signals representingthe numeral 7, etc. In this fashion, digital output signals are producedto represent different positions of the band 370 over the substrate 378and thus different positions of the object 374.

FIG. 15 shows a perspective view of apparatus for also producingdiscrete output increments representing the movement or position of aflexible band 390 and thus of an object 394. Positioned on a substrate398 are a plurality of drain regions 402 interleaved with a plurality ofsource regions 406. The drain regions 402 are connected to a commonconductor 410 and the source regions 406 are also connected to a commonconductor 414. Disposed between each adjacent drain region and sourceregion are channel regions 418 to effectively define a plurality of FETsarranged in a linear array on the substrate 398. As successive channelregions 418 are covered or uncovered by the band 390, the current flowon conductors 410 and 414 changes to thus provide an indication of theposition of the band 390 and thus of the object 394.

In FIG. 16 is a perspective view of apparatus for producing a nonlinearoutput in response to movement of a band 420. Disposed on a substrate424 is a field-effect transistor having a drain region 428, a sourceregion 432 and a channel region 436 disposed therebetween. The channelregion 436 varies in width, being widest at the opposite end of thesubstrate 424 from where the band 420 is attached and gradually taperinginwardly as it runs toward the end of the substrate to which the band isattached. The drain region 428 and source region 432 extend generallyparallel with respective sides of the channel region 436 as shown inFIG. 16. When the band 420 is moved to cover the substrate 424,increasingly wider sections of the channel region 436 are covered by theband and so the current change with movement of the band is nonlinear.Of course, the channel region 436 could be formed to taper in theopposite direction to provide a different nonlinear output with movementin the band; various other shapes for the channel region could also beselected to produce nonlinear outputs.

FIG. 17 snows an embodiment of displacement measuring apparatus whichdoes not utilize a flexible band. Rather, a wedge-shaped, electricallyenergized plate 430 is employed. The plate 430 is suspended above asubstrate 434 (for example, by being attached to an object whoseposition is to be measured) to move forward or backward in a crosswisedirection of the substrate as an object to which the plate would beattached is moved. The plate 430 is coupled to a voltage source 438 tobe energized thereby. The substrate 434 includes an FET with a sourceregion 442, channel region 446 and drain region 450. So long as theplate 430 was maintained out of contact with the substrate 434, noinsulation layer would be required, although as a precaution it wouldprobably be advisable to include it as an overlay of the substrate.

As can be seen from FIG. 17, as the plate 430 is moved in the directionof the peak of the plate (forwardly), a larger area of the plate coversthe channel region 446 of the FET and this, of course, causes a changein conduction between the source region and drain region. As the plate430 is moved in the opposite direction (rearwardly), less of the plate430 covers the channel region 446 so that again a change in conductionbetween the source and drain region occurs. This change in conduction isdetectable to determine the position of the plate 430 and thus of theobject to which it is connected.

FIGS. 18 and 19 are perspective views of other embodiments of rotationaldisplacement measuring apparatus made in accordance with the presentinvention, but not utilizing flexible bands. The apparatus of FIG. 18shows an axle or shaft 460 which would be attached to an object whoseangular position and displacement was to be measured. The shaft 460 ismounted to rotate about its long axis in a substrate 464. Mounted toextend laterally from the shaft 460 to rotate therewith is an arm 468having a wedge-shaped cross-section with the apex of the wedgedeveloping a line-charge effect directed downwardly toward the substrate464. The arm 468 is coupled to a voltage source 472 to receive anelectrical charge therefrom. Alternatively, the arm 468 could carry anelectrostatic charge for example as a result of electrons being embeddedin the arm. Disposed generally in a circle under the path of movement ofthe arm 468 are a plurality of FET sensors 476.

As the shaft 460 is rotated (because of movement of the object to whichit is connected), the arm 468 is caused to sweep over different ones ofthe sensors 476 which detect the electric field emanating from the armto thereby generate a signal indicating the position of the arm.Obviously, that sensor 476 producing the stronger signal would be thesensor over which the arm 468 is positioned.

Although the sensors 476 are shown with some spacing therebetween on asubstrate 464, the sensors could have a variety of sizes and spacing,with more sensors providing for greater sensitivity in determiningangular position of the shaft 460.

FIG. 19 also is adapted for measuring angular displacement of a shaft480 which is mounted to rotate about its long axis in a substrate 484.Mounted to rotate with the shaft 480 is a semicircular plate 488 towhich an electrical charge is supplied by a voltage source 492. Theplate 488, like the arm 468, rotates above the top surface of thesubstrate 484. Formed in the upper surface of the substrate 484 are fourFET sensors 496, 500, 504 and 508. Each of the FET sensors is formed ina semicircle (with parallel extending source, drain and channel regions)to be concentric with at least a portion of two of the other sensors.Thus, sensor 496 circumscribes a portion of sensor 500 and a portion ofsensor 508 while sensor 504 circumscribes the other parts of sensor 500and 508. As the plate 488 is rotated, it will always cover portions ofat least three of the FET sensors, and in most positions it will coverportions of all four of the sensors.

In operation, the FET sensors 496, 500,504 and-508 produce signalsindicative of the proportion of the sensor affected by the electricfield produced by the plate 488 and thus by the portion of the sensorwhich is covered by the plate. The signals, in turn, define the angularposition of the shaft 480 and thus the angular position of the object towhich the shaft is connected.

FIGS. 20, 21 and 22 all snow band-controlled transducers which utilizeoptical sensing. In FIG. 20, a light source 520 directs light downwardlytowards a substrate 524 over the top surface of which an opaque band 528is disposed to roll and unroll as an object to which the band isconnected is moved. Formed in the top surface of the substrate 524 is anelongate photocell 532 which produces an output signal supplied to adetector 536 whose magnitude is proportional to the amount of lightimpinging on the photocell. As the band 528 rolls to cover and unrollsto uncover the photocell 532, the amount of light blocked by the band,and thus the amount of light impinging upon the photocell 532 varies tothereby cause a variation in the output signal from the photocell. Thisoutput signal thus provides a measure of the position of the band 528over the photocell and thus a measure of the position of the object towhich the band is connected.

FIG. 21 shows an alternative embodiment of a displacement measuringdevice utilizing optical sensing. Here, a substrate 540 includes aplurality of light-emitting diodes 544 formed in the upper surface ofthe substrate and energized by a current source 548. A flexible, opaqueband 552 is attached at one end to one end of the upper surface of thesubstrate 540 to roll and unroll over the light-emitting diodes 544 asan object to which the band is coupled is moved. Light from thelight-emitting diodes 544 is projected upwardly, unless blocked by theband 552, to be detected by a photocell 556. As with the FIG. 20embodiment, the photocell 556 produces an output signal whose magnitudeis proportional to the amount of light impinging thereon and this outputsignal is detected by a detector 560. Thus, as the band 552 is caused toroll over and unroll from over the substrate 540 and the light-emittingdiodes 544, varying amounts of light are allowed to react the photocell556 to thereby vary the magnitude of the output signal of the photocell.This output signal thus provides an indication of the position of theband 552 over the substrate 554 and thus a measure of the position ofthe object to which the band is connected.

FIG. 22 shows a side, elevational view of another embodiment ofdisplacement measuring apparatus utilizing optical sensing. Here, asubstrate 570 includes a plurality of photocells 574 disposed on theupper surface thereof. A flexible, light-reflective band 78 is attachedat one end to one end of the upper surface of the substrate 570 to rolland unroll from over the upper surface thereof as an object 582, towhich the band is attached, is caused to move. A light source 586, forexample a laser light source, directs a beam of light 588 toward theband 578 at a location which will reflect the light beamed downwardlytowards the upper surface of the substrate 570. The light beam will thusbe caused to impinge upon one of the photocells 574 depending upon theposition of the band 578 and thus depending upon the position of theobject 582. The photocell upon which the light beam is impinging, ofcourse, produces an output signal indicating receipt of the light andsuch signal is indicative of the position of the band 578 and object582.

It should be understood that whenever photocells in the embodiments ofFIGS. 20 and 21 were shown as being a single photocell, that a series ofindividual photocells could also be utilized. Also, a series oflight-emitting diodes 544 are shown in FIG. 21, but a continuous stripof light could also be utilized.

FIG. 23 is a side, elevational view of a band-controlled transducerwhich utilizes acoustic sensing. Here, a band 590 is connected at oneend to a substrate 592 and at the other end to an object 594 whoseposition and movement is to be measured. Disposed generally at one endof the substrate 592 in the direction in which the band 590 would rolldown over the substrate is a sonar signal source 596 for transmittingacoustic signals toward the band 590, and an acoustic detector 598 fordetecting signals reflected back from the band. The detector 598 detectsthe time of travel of the acoustic signals which, of course, variesdepending upon the position of the band 590 and thus the position of theobject 594. Of course, there is no need for any substrate baseddetecting elements since the detection of the position of the band 590is accomplished by the acoustic signal source 596 and detector 598.

FIGS. 24, 25, 26, 27, 28 and 29 all show specific applications of theuse of the band-controlled transducers described earlier. FIG. 24 is agraphic view of displacement measuring apparatus of the presentinvention utilized for weighing. Here, a spring 600 interconnects amoveable element 604 to a fixed support 608. A holding plate 612 forholding an object 616 to be weighed is coupled by connecting lines 620to the moveable element 604. A substrate 624 includes a sensor formed inthe surface 628 over which a flexible band 632 is disposed to roll andunroll, as discussed in the earlier embodiments. One end of the band 632is attached to the lower end of the substrate 624 and the other end ofthe band is attached to the moveable element 604 to allow the desiredrolling and unrolling of the band. The substrate 624 with sensor 628 iscoupled to a display device 636 to provide a reading representing themagnitude of the output signal of the sensor and thus a reading of theweight of the object 616.

FIG. 25 is a side, elevational view of temperature measuring apparatus.A substrate 650 includes a sensor 654 formed in the upper surfacethereof. A flexible band 658 having a first thermal expansioncoefficient is attached at one end to one end of the substrate 650 tooverlay a portion of the substrate. A second band 662 having a secondthermal expansion coefficient overlays the first-mentioned band 658. Avoltage source 666 is coupled to the band 658 to supply a chargethereto.

As the ambient temperature to which the device of FIG. 25 is subjectedchanges, the bands 658 and 662 are caused to expand at different ratescausing the curling or uncurling of the two bands from the surface ofthe substrate 650. For example, if the thermal expansion coefficient ofband 658 is greater than that of band 662, then as the temperaturerises, the two bands will tend to curl away from the substrate 650. Ofcourse, as the band 658 rolls over or unrolls from over the sensor 654,the output signals from the sensor vary to indicate the position of theband 658 and thus the ambient temperature.

FIG. 26 shows a device for measuring the angular position between twoelongate elements 680 and 684. The elements 680 and 684 are joined atone end to pivot about a pivot point 688. Linear sensors 6.90 and 694are attached to elongate elements 680 and 684 respectively and aflexible, electrically or magnetically energized band 698 is attached atits two ends to elements 680 and 684 so that the band extends inwardly,overlaying a portion of the sensors 690 and 694 in a bow shape. As theelements 680 and 684 are pivoted closer together, more of the band 698overlays the sensors 690 and 694 and as the elements are pivoted awayfrom one another, less of the band overlays the sensors. The sensors 690and 694 detect the proximity of the band 698 to produce signalsindicating the relative positions of the elements 680 and 684, asdiscussed for the previous embodiments.

FIG. 27 shows an alternative weighing device including a substrate 704having a sensor 708 formed in the upper surface thereof. A platform 712is mounted on springs 716 and 720 to maintain a position generally inparallel with and above the substrate 704. A flexible band 724 isconnected at one end to one end of the substrate 704 and at the otherend to one end of the platform 712. When an object 728 is placed on theplatform 712 to be weighed, the platform is caused to move downwardlycloser to the substrate 704 to thus cause the band 724 to roll over andcover more of the sensor 708. The weight of the object 728 determinesthe extent to which the band 724 covers the sensor 708 and this isdetected by the sensor to provide a readout in a readout device 732 ofthe weight of the object.

FIG. 28 is a side, elevational view of an accelerometer including asubstrate 750 having a sensor 754 formed in the upper surface thereof. Aband 758 is attached as previously described to the substrate 750 and isattached at the free end to a mass 762. The mass, in turn, is coupled bya spring 766 to a rigid support member 770 which is mounted on thesubstrate 750. As the device of FIG. 28 is accelerated to the right orleft, the mass 762 is caused to move to the left or right respectivelydepending upon the magnitude of the acceleration (and stiffness of thespring 766) and this movement, in turn, causes the band 758 to roll overor unroll from over the sensor 754 which detects the movement. In thismanner, acceleration of the device of FIG. 28 can be measured. Thespring 766 restores the mass 762 to a rest position when no accelerationis taking place.

Finally, FIG. 29 shows a side, elevational view of apparatus formeasuring velocity of an object 780. When the object 780 is caused tomove left or right at a certain velocity, a band 784 to which the objectis attached is caused to roll over or unroll from over a substrate 786at one-half the velocity of movement of the object. The band is made ofa conductive material and is coupled via a resistor 788 and ammeter 790to a DC current source 792. The other side of the current source 792 iscoupled to a conductive plate 794 which is disposed on top of thesubstrate 786. A dielectric layer 796 overlays the conductive plate 794and is positioned under the band 784. The current source 792 produces acapacitance between the plate 794 and that portion of the band 784 whichis overlying the dielectric layer 796. As the object 780 is caused tomove at a certain velocity to the left or right in FIG. 29, the band 784either covers or uncovers the dielectric layer 796 at one-half thatvelocity causing a change in the capacitance between the band and theplate 794. This change, which is proportional to the velocity of theobject 780, causes a current to flow through the resistor 788 and thiscurrent is detected by the ammeter 790 to provide a measure of thevelocity of the object 780. Other arrangements for measuring currentproduced as a result of a change in capacitance could also be providedas discussed earlier.

FIGS. 30 and 31 show perspective views of displacement measuringapparatus utilizing electrical resistance variation to detect positionmovement of an object attached to the end of a flexible band. In FIG.30, the band 800 is attached at one end to roll and unroll from over asubstrate 804. The free end of the band would be attached to the object(not shown) whose movement was to be detected. Formed in the uppersurface of the substrate 804 are two resistive strips of material 808and 812 which extend generally parallel with one another in aspaced-apart relationship lengthwise on the substrate. The resistivestrip 808 is coupled to a current source 816 and the resistive strip 812is coupled to an ammeter 820 and then to the current source 816. Theband 800 is made of a conductive material so that current flows from thecurrent source 816 through that portion of the resistive strip 808 notin contact with the band, through the band to the resistive strip 812and then through the ammeter 820 back to the current source. The greeterthe length of the resistive strips 808 and 812 through which currentmust flow, the lower is the current because the resistance of the flowpath is greater, and vice versa. Thus, as the band 800 is caused to rollover or unroll from over the resistive strips 808 and 812, theresistance in the flow path is caused to change, resulting in avariation in the current flowing through the ammeter 820 and thisvariation is measured to thereby provide a measure of the position ofthe free end of the band 800. The resistive strips might illustrativelybe made of nickel-chromium deposited on polymer strips (for examplemylar) attached to the upper surface of the substrate 804.

FIG. 31 also measures the position of the free end of the band 830utilizing electrical resistance variation. Here, the band 830 isattached at one end to a substrate 834 on the upper surface of which aredisposed two conductive strips (for example, metal) 838 and 842 arrangedto be generally parallel with one another as shown. Conductive strip 838is coupled to a current source 846 and conductive strip 842 is coupledthrough an ammeter 850 to the other side of the current source. The band830 is made of a flexible, resistive material to conduct current betweenthe conductive strips 838 and 842 but to present a predeterminedresistivity. A current path is established in the FIG. 31 apparatus fromthe current source 846 through the conductive strip 838 and across thatportion of the band 830 in contact with the two conductive strips to theconductive strip 842 and then through the ammeter 850 back to thecurrent source. As the free end of the band 830 is caused to move, theband rolls over and unrolls from over the conductive strips 838 and 842to vary the total resistance of the current flow path between the twostrips and, as this resistance varies, the current through the ammeter850 is also caused to vary to thereby provide a measure of the positionof the free end of the band 830. The resistive band 830 couldillustratively be made of nickel-chromium deposited on a thin polymersheet of material, of graphite filled rubber, etc.

As described, the FIGS. 30 and 31 apparatus both measure position anddisplacement of an object connected to a flexible band by utilizingelectrical resistance variation in a current flow path.

FIG. 32 shows a side, elevational view of a type of null-band sensorapparatus in which an elongate mass or strip 860 bridges between and isattached to two conductive band loops 864 and 868. The band loop 864 ispositioned to bridge between two conductive plates 872 and 876 disposedon a substrate 874. The plates 872 and 876 are connected respectively tovoltage sources 878 and 880. The magnitude of the voltage signalsupplied by the voltage sources 878 and 880 to respective plates 872 and876 is controlled by a servologic circuit 884 which receives inputs fromsensors 886 and 888 formed in a linear spaced-apart position on theupper surface of substrate 890. The sensors 886 and 888 could be of thetypes previously described.

In operation, when the mass 860 is caused to move to the left or rightin FIG. 32, for example, by a force applied thereto, by acceleration ofthe FIG. 32 device, etc., the bands 864 and 868 are caused to roll overthe respective substrates on which they are disposed and the movement ofband 868 is sensed by the sensors 886 and 888 which signal theservologic circuit 884 accordingly. The servologic circuit 884, inresponse to the signals from the sensors, signals the voltage sources878 and 880 to produce an electrostatic attraction in a correspondingone of the plates 872 and 876 to attract the conductive band loop 864and cause it to roll back towards a rest or null position. Thus, if themass 860 had moved to the left, the plate 876 would be energized toattract the band 864 and cause it to roll back to the null positionmidway between plates 872 and 876, and vice versa. In the mannerdescribed, a null-position acceleration (or other force) sensor isprovided.

It is to be understood that the above-described arrangements are onlyillustrative of the application of the principles of the presentinvention. Numerous modifications and alternative arrangements may bedevised by those skilled in the art without departing from the spiritand scope of the present invention and the appended claims are intendedto cover such modifications and arrangements.

What is claimed is:
 1. Displacement measuring apparatus comprisinganelement whose displacement is to be measured, sensor means defining twofacing, generally parallel conducting surface areas for developing acapacitance therebetween, two dielectric layers, each disposed on arespective surface area, and adapted to produce an electrical outputsignal whose value varies with variation in proximity of a conductivemember to said surface areas, an elongate, flexible, electricallyconductive hand disposed in proximity with said surface areas so that atleast a portion of said band is caused to move non-slidably relative tosaid surface areas when the element is moved to thereby vary the valueof the output signal of said sensor means, said apparatus furthercomprising a second elongate, flexible, electrically conductive bandjoined at one end to one side of one of the dielectric layers topartially overlie the layer, said first mentioned band being joined atone end to one side of the other dielectric layer adjacent to the oneside of said one dielectric layer, to partially overlie the other layer,said bands each extending from a respective one side forwardly towardthe opposite side of a respective layer, and then curving outwardly fromthe respective layer and rearwardly to join and extend along with theother band, said other ends of the bands being caused to move toward andaway from between the dielectric layers as the element is moved tothereby cause the bands to respectively cover and uncover correspondingportions of the dielectric layers to thus vary the capacitance betweenthe surface areas.
 2. Apparatus as in claim 1 wherein said sensor meansfurther comprises electret strip means for developing an electric fieldand disposed between the band and the first and second means, whereinsaid band is grounded, and wherein said first and second means comprisefield-effect transistors for detecting the magnitude of the electricfield impinging on the transistors.
 3. Displacement measuring apparatuscomprisingan element whose displacement is to be measured, sensor meansformed with at least one surface area and adapted to produce anelectrical output signal whose value varies with variation in proximityof a conductive member to said surface area, wherein said sensor meanscomprises means defining a nonconducting surface area arranged in afacing relationship with said one surface area, a flexible band beingjoined at one end to one side of the nonconducting surface area toextend forwardly over a portion of the nonconducting surface area andthen curve outwardly therefrom and rearwardly so that as the element ismoved, the other end of the band is caused to move toward or away frombetween the nonconducting surface area and said one surface area, meansfor developing a capacitance between said one surface area and thatportion of the band which is curved to extend rearwardly, saidcapacitance varying as the area of the rearwardly extending portion ofthe band varies and thus as the other end of the band is caused to movetoward or away from between the nonconducting surface area and said onesurface area, means for measuring the capacitance developed between theband and said one surface area, and the elongate, flexible, electricallyconductive band disposed in proximity with said surface area so that atleast a portion of said band is caused to move non-Slidably relative tosaid surface area when the element is moved to thereby vary the value ofthe output signal of said sensor means.
 4. Displacement measuringapparatus comprisingan element whose displacement is to be measured,wherein said element comprises a cylinder, and wherein an elongate,flexible, electrically conductive band is formed into a loop, an outsidesurface of which is disposed in contact with the cylinder, sensor meansformed with at least one surface area, said at least one surface areacomprising a substrate having a first surface area disposed in contactwith an opposite outside surface area of the band so that as thecylinder is rotated, the band is caused to roll over the first surfacearea, and wherein the sensor means is adapted to produce an electricaloutput signal whose value varies with variation in proximity of aconductive member to said surface area, the elongate, flexible,electrically conductive band disposed in proximity with said surfacearea so that at least a portion of said band is caused to movenon-slidably relative to said surface area when the element is moved tothereby vary the value of the output signal of said sensor means, andmeans disposed at the first surface area for detecting the location ofthe band on the first surface area and thus the degree of rotation ofthe cylinder.
 5. Apparatus as in claim 4 wherein said detecting meanscomprises first and second means linearly spaced apart on the firstsurface area along the direction of roll of the band for producing firstand second output signals respectively, representing the portions of thefirst and second means covered by the band.
 6. Apparatus as in claim 4wherein said first surface area is shaped to surround the cylinder. 7.Apparatus as in claim 6 wherein said first surface area is shapedgenerally in the form of a hollow cylinder.
 8. Apparatus as in claim 4wherein said first surface area is generally planar.
 9. Apparatus as inclaim 4 wherein said detecting means comprisesmeans defining two facing,conducting surface areas, one located on the first surface area of thesubstrate and the other located on the surface of said cylinder, fordeveloping a capacitance there between, two dielectric layers, eachdisposed on a respective conducting surface area, with the bandgenerally disposed therebetween, and means for producing an outputsignal indicative of said capacitance which varies depending upon theportion of the band disposed between the two conducting surface areasand the magnitude of the areas of said surface areas disposed oppositelyone another.
 10. Apparatus as in claim 4 wherein said sensor meansfurther comprises means for causing the band to produce an electric ormagnetic field which emanates from the band, and wherein said detectingmeans comprises a semiconductor means for detecting the magnitude of theelectric or magnetic field impinging on the semiconductor means. 11.Displacement measuring apparatus comprisingan element whose displacementis to be measured, sensor means which comprises first and second facingsubstrates and adapted to produce an electrical output signal whosevalue varies with variation in proximity of a conductive member to saidfirst and second facing substrates, each having a generally planarsurface area which faces the surface area of the other substrate, saidfirst substrate including linearly spaced-apart first and second meansdisposed on the surface area of the first substrate for producing firstand second output signals respectively, representing the portions of thefirst and second means covered by a flexible band, said second substratebeing coupled to said element and including linearly spaced-apart thirdand fourth means disposed on the surface area of the second substratefor producing third and fourth signals respectively, representing theportions of the third and fourth means covered by said band, whereinsaid band is formed into a loop, a lower portion of which is attached tothe surface area of the first substrate between the first and secondmeans and in contact with the surface area of the second substrate toallow the band to be selectively flexed to cover and uncover at leastportions of said first and second means and said third and fourth meansas the element and thus the second substrate is moved relative to thefirst substrate in a plane defined by the first, second, third andfourth means, and the elongate, flexible, electrically conductive banddisposed in proximity with said first and second facing substrates sothat at least a portion of said band is caused to move non-slidablyrelative to said first and second facing substrates when the element ismoved to thereby vary the value of the output signal of said sensormeans.
 12. Apparatus for weighing objects and comprisingan element whosedisplacement is to be measured, sensor means formed with at least onesurface area and adapted to produce an electrical output signal whosevalue varies with variation in proximity of a conductive member to saidsurface area, an elongate, flexible, electrically conductive banddisposed in proximity with said surface area so that at least a portionof said band is caused to move non-slidably relative to said surfacearea when the element is moved to thereby vary the value of the outputsignal of said sensor means, a platform on which objects to be weighedmay be placed, said platform being attached to the element to cause theelement to move from a rest position relative to the sensor means whenobjects are placed on the platform, resilient means attached to theplatform for causing the platform to return to the rest position when anobject is removed from the platform, and display means coupled to thesensor means for producing a display indicating the value of the outputsignal of the sensor means.
 13. Apparatus for weighing objects andcomprisingan element whose displacement is to be measured, sensor meansformed with at least one surface area and adapted to produce anelectrical output signal whose value varies with variation in proximityof a conductive member to said surface area; an elongate, flexible,electrically conductive band disposed in proximity with said surfacearea so that at least a portion of said band is caused to movenon-slidably relative to said surface area when the element is moved tothereby vary the value of the output signal of said sensor means,wherein one end of said band is fixed relative to the sensor means tooverlie said one surface area, said band being composed of a materialhaving a first thermal expansion coefficient, said apparatus furtherincluding a second band overlying and joined to the first-mentioned bandand being composed of a material having a second thermal expansioncoefficient which is different from the first thermal coefficient ofexpansion so that as the temperature of the two bands changes in onedirection, one band changes length more than the other to cause theother end of the first band to curl away from the surface area anduncover a portion of the area proportional in size to the change intemperature, and as the temperature of the two bands changes in theother direction, the said other end of the first band is caused touncurl towards the first surface area.
 14. Apparatus for measuring theangle between at least two elements and comprisinga first element, asecond element pivotally joined at one end to one end of the firstelement, sensor means formed with at least one surface area and adaptedto produce an electrical output signal whose value varies with variationin proximity of a conductive member to said surface area, wherein saidsensor means is disposed on the first element, said apparatus furtherincluding a second sensor means formed with a surface area and adaptedto produce an electrical output signal whose value varies with variationin proximity of an elongate, flexible, electrically conductive band tothe surface area of the second sensor means, said second sensor meansbeing disposed on the second element, and wherein said band is fixed atone end to the first-mentioned sensor means and at the other end to thesecond sensor means so that the band overlies at least a portion of thesurface areas of the first and second sensor means and bows inwardlytoward the pivot joint of the first and second sensor means beinguncovered and covered as the first and second elements are pivoted awayand toward one another respectively, and the elongate, flexible,electrically conductive band disposed in proximity with said surfaceareas so that at least a portion of said band is caused to movenon-slidably relative to said surface areas when the elements are movedto thereby vary the value of the output signal of said sensor means. 15.Apparatus for measuring acceleration, and comprisingsensor means formedwith at least one surface area and .adapted to produce an electricaloutput signal whose value varies with variation in proximity of aconductive member to said surface area; an elongate, flexible,electrically conductive band disposed in proximity with said surfacearea so that at least a portion of said band is caused to movenon-slidably relative to said surface area when the element is moved tothereby vary the value of the output signal of said sensor means, and anelement whose acceleration is to be measured, wherein said elementcomprises a predetermined mass of material, and wherein one end of saidband is fixed relative to said sensor means and the other end is coupledto said mass of material so that the band is caused to selectively coverand uncover at least a portion of said surface area as the mass ofmaterial is moved, said apparatus further including biasing meanscoupled between the mass of material and the sensor means to urge themass of material to a rest position when the apparatus is not beingaccelerated, and to allow movement of the mass of material and thus amovement of the band in proportion to the magnitude of acceleration,when the apparatus is accelerated.
 16. Apparatus for measuring velocityof an element, and comprisingsensor means formed with at least onesurface area and adapted to produce an electrical output signal whosevalue varies with variation in proximity of a conductive member to saidsurface area; an elongate, flexible, electrically conductive banddisposed in proximity with said surface area so that at least a portionof said band is caused to move non-slidably relative to said surfacearea when the element is moved to thereby vary the value of the outputsignal of said sensor means, and the element whose velocity is to bemeasured, wherein one end of said band is fixed relative to said sensormeans and the other end is coupled to the element so that the band iscaused to selectively cover and uncover at least a portion of saidsurface area as the element is moved, and wherein said sensor meanscomprises a conductive plate located at said first surface area underthe band, a dielectric layer of material overlying said conductiveplate, and a current source, current measuring means and a resistorconnected in series between the band and conductive plate to develop acapacitance between the plate and band whose magnitude is proportionalto the portion of the plate covered by the band, said magnitude varyingin proportion to the velocity of covering or uncovering the conductiveplate by the band and thus in proportion to the velocity of the element,said variation in capacitance causing current to flow at a magnitudeproportional to the variation in capacitance to thus provide a measureof the velocity of the element.